CN111557859A - Pyrophyllite loaded nano ZnO composite uvioresistant agent and preparation method thereof - Google Patents

Abstract

The invention relates to a pyrophyllite loaded nano ZnO composite uvioresistant and a preparation method thereof, wherein natural flaky mineral pyrophyllite is used as a carrier mineral raw material, a room-temperature solid-phase synthesis method is adopted, and the 1 st step is that a mixed material is weighed and ground according to the mass ratio of 2-5: 1 of zinc sulfate heptahydrate to pyrophyllite mineral raw material to prepare a zinc sulfate heptahydrate-pyrophyllite mixture; weighing and grinding the mixed material according to the molar ratio of zinc sulfate heptahydrate to sodium oxalate being 1-2: 1 to prepare a precursor zinc oxalate-pyrophyllite mixture; 3, adopting a centrifugal washing device to centrifugally wash and remove impurities in the precursor zinc oxalate-pyrophyllite mixture; 4, drying the materials by adopting a drying device at the drying temperature of 105 ℃ for 3-6 h; and 5, roasting the loaded and dried material by adopting a roasting device, wherein the heating rate is 10-15 ℃/min, the roasting temperature is 400-550 ℃, and the temperature is kept for 2-4 h to obtain the pyrophyllite loaded nano ZnO composite uvioresistant agent. The method has the advantages of obvious effect, good safety, simple process, easy popularization and application, wide application and remarkable social and economic benefits.

Description

Pyrophyllite loaded nano ZnO composite uvioresistant agent and preparation method thereof

1. Field of the invention

The invention relates to a pyrophyllite loaded nano ZnO composite uvioresistant agent and a preparation method thereof.

2. Background of the invention

2.1 ultraviolet concept

Ultraviolet (UV) is an electromagnetic wave having a wavelength of 200nm to 400 nm. The ultraviolet rays in the sunlight can be divided into three sections of long-wave ultraviolet ray UVA (320-400 nm), medium-wave ultraviolet ray UVB (280-320 nm) and short-wave ultraviolet ray UVC (200-280 nm) according to the wavelength. Proper sunlight irradiation can increase oxygen content of organism cells, reduce blood sugar and cholesterol content, and enhance human vitality. However, when the sun is excessively exposed for a long time, various skin diseases such as sunburn, freckle, acne and the like are easily induced and aggravated, and internal organs of the body are damaged in severe cases. The basic characteristics of the uv segments are now collated as shown in table 1.

TABLE 1 classification and characterization of UV

The short wave ultraviolet UVC is absorbed by the ozone layer, cannot reach the ground and has no effect on human bodies. The energy of the medium-wave ultraviolet UVB is highest, and the great part of the energy is absorbed by the skin dermis to cause the dermal blood vessels to expand and present the symptoms of red swelling, blisters and the like. If the skin is subjected to UVB irradiation for a long time, the skin can generate erythema, inflammation and skin aging, and skin cancer can be seriously caused. In daily life, 95% or more of ultraviolet rays which the skin comes into contact with are UVA, the penetration force is strong, the skin is photo-aged, skin cancer is caused, and UVA attracts people gradually in recent years.

Ultraviolet rays not only cause harm to human bodies, but also have certain damage and aging effects on coatings, plastics, printing ink and other high polymer materials, so that the high polymer materials have the phenomena of light loss, fading, yellowing, cracking, peeling, embrittlement, pulverization, strength reduction, delamination and the like. Even indoor light and sunlight transmitted through a glass window can degrade some materials.

Therefore, ultraviolet rays have considerable harm to human health, high polymer materials and the like, so that the research and application of the ultraviolet resistant agent or the ultraviolet shielding material have very important practical significance.

2.2 research and State of the Art ultraviolet Shielding materials

Since the discovery of the hazards of ultraviolet light by humans, some means have been taken to shield ultraviolet light. Ultraviolet shielding materials for human skin protection are mainly of two types: one category is ultraviolet resistant textiles including sun protection clothing, sun protection hats, sun protection gloves, and sun protection umbrellas, among others. The ultraviolet resisting paint is a kind of ultraviolet resisting paint, and is a kind of sunscreen skin care product or cosmetics used in daily life. The ultraviolet shielding material for protecting the high polymer material is mainly a filler with an ultraviolet shielding function, but the research on the aspect is relatively weak.

The anti-ultraviolet agent in skin care products or cosmetics means a substance which can effectively absorb or scatter solar radiation, can reduce damage to the skin, and can effectively absorb or scatter long-wave ultraviolet rays (UVA) and medium-wave ultraviolet rays (UVB) in sunlight. They can be divided into physical and chemical sunscreens by their protective mechanism of action, also commonly referred to as inorganic and organic sunscreens, respectively.

Chemical sunscreens (organic sunscreens), also known as uv absorbers, are primarily organic compounds which absorb harmful uv radiation. Among them, tert-butyl methoxydibenzoylmethane is the most representative UVA segment ultraviolet absorbent in the current sunscreen cosmetics, and isooctyl methoxycinnamate is the most widely used UVB segment ultraviolet absorbent in the current sunscreen cosmetics. However, organic sunscreens tend to act only in a single wavelength band (UVA or UVB) and may also decompose and lose their sunscreen effect under the action of light, with a short period of effectiveness. In contrast, inorganic sunscreens (physical sunscreens) are more stable and safer, and they achieve the goal of sunscreening by primarily scattering ultraviolet light while absorbing ultraviolet light in small amounts. Inorganic sunscreens are increasingly widely used due to their advantages of high efficiency, safety, durability, etc.

Current inorganic sunscreens (physical sunscreens) are predominantly TiO₂And ZnO, both of which are semiconductor materials, TiO₂Mainly aiming at UVB protection, ZnO mainly shields UVA. But the sun-screening and ultraviolet screening effects of the two are closely related to the particle size or nanometer effect of the two. The results of the previous study show that when both are nanoparticles, i.e. TiO₂When the particle size is 30-50 nm (grandma et al, 1998) and the particle size of ZnO is 10-35 nm, the nano effect is prominent, and the sunscreen ultraviolet shielding effect is excellent (YaoOer et al, 2003).

Nanometer ZnO is used as a widely used physical sun-screening agent, the principle of shielding ultraviolet rays is to absorb and scatter the ultraviolet rays, and the nanometer ZnO has the characteristics of small particle size, large specific surface area, good stability, small irritation and the like; in addition to good ultraviolet shielding performance, the antibacterial ultraviolet shielding material also has the advantages of safety, stability, heat resistance, certain antibacterial property and the like, so the antibacterial ultraviolet shielding material is widely applied to the field of sunscreen skin care products or cosmetics in recent years.

However, as the nano ZnO has the characteristics of weak polarity and tiny nano particles and high surface energy, the nano particles are in a thermodynamic unstable state and tend to agglomerate, thereby limiting the exertion of the nano effect and the ultraviolet shielding effect. In addition, in the process of manufacturing skin care products or cosmetics, nano ZnO particles are difficult to disperse to the original particle size, the ultraviolet absorption effect in the UVA, UVB, and UVC bands is reduced, the transparency and ultraviolet shielding performance thereof cannot be sufficiently exhibited, and the effect as a sunscreen agent in practical use is not good. In summary, as an inorganic sunscreen agent, the nano ZnO has the following main problems:

(1) agglomeration problem: the nano ZnO has high surface energy, and the particles tend to agglomerate.

(2) The problem of delamination: emulsifier for sunscreen productsThe density is about 0.96-1.1 g/cm³And the density of the nano ZnO is about 5.6g/cm³Therefore, when the nano ZnO with high density is mixed into the emulsifier, the nano ZnO is easy to precipitate, and the delamination phenomenon is generated. The layering phenomenon greatly limits the use efficiency of the nano ZnO material, and the nano ZnO material cannot be directly mixed with common cosmetics for use. If the dispersion is used alone, the dispersion and the dispersion can be separated into layers, and the dispersion must be shaken well before being used. This not only causes inconvenience to the user but also increases the use cost.

(3) Health problems are as follows: the nanometer ZnO in the sunscreen product is easy to gather at the horny layer of the skin of a human body, the opening of the sebaceous gland of hair follicle and the wrinkle, and the size of the facial pore of the human body is generally 20 mu m, so the nanometer ZnO is easy to block the skin pore after long-term use, is not beneficial to the secretion of sweat and is easy to cause skin infection. Furthermore, trace amounts of zinc may also be absorbed through the skin into the blood, which is very detrimental to human health, especially in sunburn and skin-damaged patients.

(4) The aesthetic problem is that: due to the aggregation of the nano ZnO, the phenomenon of unnatural whitening can be generated when the nano ZnO is smeared on the skin, and the aesthetic effect is influenced.

(5) Environmental problems: zn²⁺The dissolution and the generation of active oxygen may have certain influence on the environment and the ecosystem and are not easy to recycle.

(6) The price problem is as follows: because the nano ZnO can not be directly mixed with common cosmetics for use, in order to overcome the layering phenomenon of dispersion liquid when the nano ZnO is used alone, a small-sized special container and a device are needed in actual use, the production and use cost of physical sun-proof products is greatly increased, the market condition of the products is generally higher, and the using amount of the products is limited.

2.3 Current State of the Art for the preparation of Nano ZnO

The preparation method of nano ZnO mainly comprises three types, namely a liquid phase method, a solid phase method and a gas phase method according to different states of raw materials and preparation processes. Among them, the gas phase method is not suitable for wide application due to the disadvantages of harsh reaction conditions, high production cost, low product purity, etc. At present, the liquid phase method and the solid phase method are mainly adopted for preparing the nano ZnO, and the main advantages and disadvantages are shown in the table 2.

TABLE 2 advantages and disadvantages of the main preparation method of nano ZnO

2.4 research technical status of mineral-loaded nano ZnO composite uvioresistant agent

The problems of nano ZnO agglomeration, delamination and the like are solved, and the method can be started from two aspects: firstly, a certain preparation method is adopted to modify nano ZnO, regulate and control the shape of the nano ZnO and the like; firstly, the mineral is used as a carrier to load nano ZnO. The leading research progress of the predecessors was as follows:

US 6086666 discloses a method for preparing a flaky mineral loaded nano ZnO anti-ultraviolet material by a hydrolysis precipitation method, which is characterized in that a zinc source and a precipitator are added into an aqueous solution of minerals at a certain reaction temperature for reaction, and after a certain time, the mixture is filtered, dried and calcined to obtain the anti-ultraviolet composite material, wherein the flaky material can be muscovite, sericite, talc and kaolinite.

CN 104017393a discloses a method for preparing nano ZnO-coated sericite powder composite material by direct precipitation, which is characterized in that in an aqueous solution system, calcium hydroxide or calcium oxide is added into a mixed system of sericite powder and zinc sulfate solution to directly obtain the nano ZnO-coated sericite powder composite material. The obtained composite material has good dispersibility in an organic solvent, and has excellent uvioresistant performance and antibacterial and deodorant performance.

Gongmeizhuo, Zhengshuilin, etc. (2017) mention that the hydrolytic precipitation method is adopted to coat nano ZnO on the surface of calcined kaolin to prepare the nano ZnO/calcined kaolin composite anti-ultraviolet powder material, and the composite powder material has good anti-ultraviolet performance under the proper preparation conditions, namely, the coating amount is 8%, the reaction temperature is 90 ℃, the modification time is 10min, the pulp concentration is 10:1, and the calcination temperature is 400 ℃.

From the above description, the preparation method adopted in the prior art for the mineral-supported nano ZnO is mainly a liquid phase method. According to the search of the inventor, no technical result report of preparing the pyrophyllite-loaded nano ZnO composite uvioresistant agent by adopting a room-temperature solid-phase synthesis method exists at present.

3. Technical scheme

The invention aims to prepare a composite uvioresistant agent or an ultraviolet shielding material by taking natural flaky mineral pyrophyllite with a layered structure as a raw material and loading nano ZnO, so as to overcome the problems of easy agglomeration, easy delamination, poor dispersibility and the like of the existing nano ZnO, improve the sun-proof and ultraviolet shielding performances, improve the aesthetic effect, prevent the whitening phenomenon, improve the use efficiency and reduce the use cost. To achieve the above object, the following technical problems must be solved:

(1) selection of carrier mineral raw materials: the layered structure silicate minerals are of various types, and the selection conditions are as follows: has a layered structure and two-dimensional habit crystals, and mineral crystals are mainly in a fine scale shape, are non-toxic and harmless, and have rich mineral raw materials.

(2) Selecting a preparation method of nano ZnO: as shown in Table 2, several methods of the present invention have advantages and disadvantages, and the selection conditions of the preparation method of the present invention are: no toxicity and harm, convenience and feasibility and good effect.

(3) The preparation process of the room temperature solid phase synthesis method of nano ZnO comprises the following steps: on the basis of the work in the step (2), the process conditions for preparing the nano ZnO by the room-temperature solid-phase synthesis method are further determined by experiments.

(4) The preparation process of the pyrophyllite loaded nano ZnO composite uvioresistant agent comprises the following steps: on the basis of the work in the step (3), the process conditions for preparing the pyrophyllite-loaded nano ZnO composite uvioresistant agent by adopting a room-temperature solid-phase synthesis method are further determined through experiments.

The specific technical scheme is as follows:

3.1 selection of Carrier mineral raw materials

Pyrophyllite is a 2:1 type dioctahedral lamellar structure aluminosilicate mineral with a crystal chemical formula of Al₂[Si₄O₁₀](OH)₂Theoretical chemical composition is Al₂O₃28.3％，SiO₂66.7% and H₂And 5.0 percent of O. The pyrophyllite is monoclinic or triclinic, and has a crystal structure consisting of two layers of SiO₄]Tetrahedron and a layer of [ AlO₆]Octahedron structure, with a typical 2:1 layered structure.Due to the restriction of a crystal layer-shaped structure, the pyrophyllite is generally scaly, has fine texture, waxy luster and smooth feel, is non-toxic and harmless, has stable chemical properties, and meets the requirement of serving as a nano ZnO carrier mineral.

FIG. 1 is an X-ray powder diffraction pattern (XRD) of a pyrophyllite sample adopted by the present invention, and it can be seen that the diffraction peak of the pyrophyllite is relatively sharp, which indicates that the pyrophyllite crystal structure as a raw material is complete, the crystallization state is good, and the pyrophyllite crystal structure is basically consistent with a pyrophyllite standard card (PDF: 46-1308), and the characteristic peaks are as follows:

moreover, almost no impurity peak appears on the XRD spectrum, which indicates that the pyrophyllite sample has high purity.

Table 3 shows the results of X-ray fluorescence spectroscopy (XRF) tests of the chemical components of the pyrophyllite sample used in the present invention, and it can be seen that the weight percentage (%) of the chemical components of the pyrophyllite sample is closer to the theoretical components, and the other impurities are very low and do not contain harmful and toxic impurities. And the XRD analysis result is combined, so that the experimental sample is relatively pure, belongs to a pyrophyllite single mineral aggregate, and meets the selection condition of a carrier mineral raw material.

TABLE 3X-ray fluorescence Spectroscopy (XRF) measurements of the chemical composition of pyrophyllite samples (in weight percent,%)

Substance(s)	SiO2	Al2O3	Fe2O3	TiO2	CaO	MgO	K2O	Na2O	MnO	P2O5	SO3	H2O
													Content (wt.)	67.96	26.73	0.07	0.24	0.09	—	0.08	0.21	—	0.09	0.06	4.49

It should be noted that the pyrophyllite mineral raw material may contain small or trace amounts of quartz, dickite, kaolinite, sericite, and the like. According to the useful chemical composition Al₂O₃And the content of impurities, mixing the leavesThe ore types of the kerolite mineral feedstock are divided into three categories: high-alumina pyrophyllite (Al)₂O₃Greater than 25 percent) and medium aluminum pyrophyllite (Al)₂O₃> 18%) and low-aluminum pyrophyllite (Al)₂O₃< 18%); or three stages, namely: glass fiber grade, ceramic grade and filler grade.

3.2 selection of preparation method of Nano ZnO

According to related documents, the invention adopts five methods shown in Table 2, prepares nano ZnO under optimized conditions, and further detects and analyzes the ultraviolet shielding performance of the nano ZnO by adopting an ultraviolet-visible light spectrophotometer, and the result is shown in figure 2.

According to the purpose and requirement of the invention, the ultraviolet resistant agent or the ultraviolet shielding material not only ensures higher absorbance of the ultraviolet region, but also ensures high transmittance of the visible region. As can be seen from FIG. 2, the industrial ZnO particles are coarse, and the UV shielding performance is poor, which is not satisfactory. The standard for distinguishing the ultraviolet resistance of domestic products at present is divided into the following parts according to the ultraviolet shielding rate: class a, the ultraviolet shielding rate is more than 90 percent; b level, ultraviolet shielding rate is 80-90%; c level, and the ultraviolet shielding rate is 50-80%. The ultraviolet resistant agent or ultraviolet shielding material should be selected from a class a as appropriate. As shown in figure 2, the ultraviolet screening rate of the nano ZnO prepared by the room temperature solid phase synthesis method is more than 90 percent, belongs to a grade and meets the requirement of the invention.

Room temperature solid phase synthesis method preparation process of 3.3 nano ZnO

The invention further determines the technological conditions for preparing the nano ZnO by the room temperature solid phase synthesis method through experiments, and the technological conditions are as follows:

(1) preparing a precursor zinc oxalate: weighing zinc sulfate heptahydrate (ZnSO) according to the molar ratio of 1-2: 1₄·7H₂O) and sodium oxalate (Na)₂C₂O₄) And further grinding and mixing for 30-40 min to obtain a precursor zinc oxalate (ZnC)₂O₄·2H₂O)；

(2) Washing to remove impurities: carrying out centrifugal washing on the precursor zinc oxalate by adopting a centrifugal washing device, washing with distilled water twice, and washing with absolute ethyl alcohol twice to remove impurities;

(3) drying the materials: transferring the washed and impurity-removed precursor zinc oxalate into a drying device, wherein the drying temperature is 105 ℃, and the drying time is 3-6 h;

(4) roasting synthesis: heating the dried precursor zinc oxalate to 400-550 ℃ by adopting a roasting device in an air environment at the heating rate of 10-15 ℃/min, and preserving the heat for 2-4 h to obtain the nano ZnO.

FIG. 3 is the X-ray powder diffraction pattern of nano ZnO prepared by room temperature solid phase synthesis, and it can be seen that three standard strong peaks with sharp peak shape and high intensity appear in the range of 30-40 degree diffraction angle, namely

This is essentially coincident with the nano ZnO standard PDF card (36-1451). Considering that the characteristic peaks appearing in the whole angle diffraction range are relatively sharp, the nano ZnO sample has a relatively good crystal form and relatively complete crystallization. Meanwhile, no miscellaneous peak which can not correspond to the standard card appears in the diffraction pattern, which indicates that the purity of the sample is higher.

FIG. 4 is a scanning electron microscope analysis photo of nano ZnO prepared by room temperature solid phase synthesis, which shows that the nano ZnO powder crystal grain is spherical or quasi-spherical, has the characteristics of nano particles, the particle size is 30 nm-50 nm, but the agglomeration phenomenon is more obvious.

3.4 preparation process of pyrophyllite-loaded nano ZnO composite uvioresistant agent

On the basis of the work, the process conditions for preparing the pyrophyllite loaded nano ZnO composite uvioresistant agent by adopting a room-temperature solid-phase synthesis method are further determined by experiments, and specifically comprise the following steps:

(1) preparing a zinc sulfate heptahydrate-pyrophyllite mixture: zinc sulfate heptahydrate (ZnSO)₄·7H₂O) and pyrophyllite mineral raw material in a mass ratio of 2-5: 1, respectively weighing a certain mass of zinc sulfate heptahydrate and pyrophyllite mineral raw material powder, and further grinding and mixing for 30-40 min to obtain a zinc sulfate heptahydrate-pyrophyllite mixture;

(2) preparation of a precursor zinc oxalate-pyrophyllite mixture: weighing a certain mass of sodium oxalate (Na) according to the molar ratio of zinc sulfate heptahydrate to sodium oxalate of 1-2: 1₂C₂O₄) Adding the mixture into a heptahydrate zinc sulfate-pyrophyllite mixture, and continuously grinding for 50-60 min to obtain a precursor zinc oxalate (ZnC)₂O₄·2H₂O) -pyrophyllite mixture;

(3) washing to remove impurities: carrying out centrifugal washing on a precursor zinc oxalate-pyrophyllite mixture by adopting a centrifugal washing device, washing with distilled water twice, and washing with absolute ethyl alcohol twice to remove impurities;

(4) drying the materials: transferring the washed and impurity-removed precursor zinc oxalate-pyrophyllite mixture into a drying device, wherein the drying temperature is 105 ℃, and the drying time is 3-6 h;

(5) roasting and loading: heating the dried precursor zinc oxalate-pyrophyllite mixture to 400-550 ℃ at the heating rate of 10-15 ℃/min in an air environment by adopting a roasting device, and preserving the heat for 2-4 h to obtain the pyrophyllite loaded nano ZnO composite uvioresistant agent.

4. Technical advantages

(1) The effect is obvious. The pyrophyllite-loaded nano ZnO composite uvioresistant agent is prepared by taking pyrophyllite as a carrier and adopting a room-temperature solid-phase synthesis method, and the composite material has better uvioresistant performance or ultraviolet shielding performance than nano ZnO prepared independently, has better dispersibility in a solvent and higher transmittance for visible light, and solves the problems of agglomeration, layering, attractiveness and the like of nano ZnO.

(2) The safety is good. The pyrophyllite used in the invention is a natural mineral, and is non-toxic and pollution-free. The raw material reagents used in the process of preparing the nano ZnO are nontoxic, safe and reliable.

(3) The process is simple. The room temperature solid phase synthesis method used by the invention has simple operation and convenient work.

(4) Easy popularization and application. The invention has simple process, convenient operation and easy learning, mastering, popularization and application.

(5) Has wide application and remarkable economic and social benefits. With the recognition of the harm of ultraviolet rays to human bodies, ultraviolet resistant materials are receiving more and more attention, and especially, compared with chemical ultraviolet resistant agents, physical ultraviolet resistant agents are safer and more stable. The pyrophyllite loaded nano ZnO composite uvioresistant agent prepared by the invention better solves the technical problems of agglomeration of the current nano ZnO and the like, has important significance for the development of the uvioresistant material industry, and has wide application prospect and remarkable economic and social benefits.

5. Description of the drawings

FIG. 1: the X-ray powder crystal diffraction spectrogram of the pyrophyllite sample adopted by the invention.

FIG. 2: the ultraviolet shielding performance (Abs-absorbance and T-ultraviolet shielding rate) of the nano ZnO prepared by different methods.

FIG. 3: x-ray powder diffraction spectrum of nano ZnO prepared by room temperature solid phase synthesis.

FIG. 4: scanning electron microscope analysis photo of nano ZnO prepared by room temperature solid phase synthesis method.

FIG. 5: x-ray powder diffraction spectra of pyrophyllite, nano ZnO and pyrophyllite loaded nano ZnO composite uvioresistant agent.

FIG. 6: scanning electron microscope analysis photos of the pyrophyllite (a) and the pyrophyllite loaded nano ZnO uvioresistant agent (b).

FIG. 7: pyrophyllite, industrial ZnO, nano ZnO, and ultraviolet-visible light spectrum contrast chart (Abs-absorbance, T-ultraviolet shielding rate) of pyrophyllite-loaded nano ZnO composite ultraviolet resistant agent.

6. Detailed description of the preferred embodiments

Example 1: pyrophyllite loaded nano ZnO composite uvioresistant agent and preparation method thereof

The pyrophyllite load nanometer ZnO composite uvioresistant agent is prepared by a room temperature solid phase synthesis method, wherein natural flaky mineral pyrophyllite is used as a carrier mineral raw material, the pyrophyllite mineral raw material is a pyrophyllite single mineral aggregate (figure 1), a crystal is in an irregular flaky shape, the scale size is 2-5 mu m (figure 6a), and the chemical components are shown in table 3, and the preparation process comprises the following 5 steps:

(1) preparing a zinc sulfate heptahydrate-pyrophyllite mixture: zinc sulfate heptahydrate (ZnSO)₄·7H₂O) and pyrophylliteWeighing a certain mass of heptahydrate zinc sulfate and pyrophyllite mineral raw material powder respectively according to a mineral raw material mass ratio of 2-5: 1, and further grinding and mixing for 30-40 min to obtain a heptahydrate zinc sulfate-pyrophyllite mixture;

(2) preparation of a precursor zinc oxalate-pyrophyllite mixture: weighing a certain mass of sodium oxalate (Na) according to the molar ratio of zinc sulfate heptahydrate to sodium oxalate of 1-2: 1₂C₂O₄) Adding the mixture into a heptahydrate zinc sulfate-pyrophyllite mixture, and continuously grinding for 50-60 min to obtain a precursor zinc oxalate (ZnC)₂O₄·2H₂O) -pyrophyllite mixture;

(3) washing to remove impurities: carrying out centrifugal washing on a precursor zinc oxalate-pyrophyllite mixture by adopting a centrifugal washing device, washing with distilled water twice, and washing with absolute ethyl alcohol twice to remove impurities;

(4) drying the materials: transferring the washed and impurity-removed precursor zinc oxalate-pyrophyllite mixture into a drying device, wherein the drying temperature is 105 ℃, and the drying time is 3-6 h;

(5) roasting and loading: heating the dried precursor zinc oxalate-pyrophyllite mixture to 400-550 ℃ at the heating rate of 10-15 ℃/min in an air environment by adopting a roasting device, and preserving the heat for 2-4 h to obtain the pyrophyllite loaded nano ZnO composite uvioresistant agent.

The detection result shows that the pyrophyllite loaded nano ZnO composite uvioresistant agent obtained by the method of the embodiment has the following characteristics:

(1) fig. 6 is an X-ray powder diffraction pattern of the pyrophyllite, nano ZnO and pyrophyllite-loaded nano ZnO composite anti-ultraviolet agent, and it can be seen that, compared with pyrophyllite and nano ZnO, characteristic peaks of pyrophyllite and nano ZnO can be seen in an XRD pattern of the pyrophyllite-loaded nano ZnO composite anti-ultraviolet agent, and since no new peak is generated, the physical composition of the pyrophyllite and the nano ZnO is illustrated.

(2) Fig. 5 is a Scanning Electron Microscope (SEM) photograph of pyrophyllite (a) and pyrophyllite-loaded nano ZnO uvioresistant agent (b), and it can be seen that nano ZnO particles are loaded on the surface of the pyrophyllite flakes, the particle size distribution is uniform, the pyrophyllite flakes are spherical, the size of the pyrophyllite flakes is about 30nm to 50nm, and the agglomeration phenomenon is obviously improved.

(3) Fig. 7 is a comparison graph of ultraviolet-visible light spectra of pyrophyllite, industrial ZnO, nano ZnO, and pyrophyllite-supported nano ZnO composite anti-ultraviolet agent, and it can be seen that: first, pyrophyllite and industrial ZnO have poor uv resistance and do not meet the performance requirements for uv resistance agents. Secondly, compared with industrial ZnO, the absorbance of the nano ZnO in an ultraviolet region is obviously increased, the ultraviolet resistance is excellent, the ultraviolet shielding rate can reach 95%, the transmittance in a visible light region is lower, and the whiteness is lower than that of the industrial ZnO. Thirdly, compared with nano ZnO, the pyrophyllite loaded nano ZnO uvioresistant agent has the advantages that the absorbance of the ultraviolet region is further improved, the ultraviolet shielding rate is close to 99%, the uvioresistant performance is excellent, the transmittance of the pyrophyllite loaded nano ZnO uvioresistant agent to visible light is superior to that of the prepared nano ZnO, and the transparency of the pyrophyllite loaded nano ZnO uvioresistant agent is good.

The detection results show that the pyrophyllite-loaded nano ZnO composite uvioresistant agent obtained by the embodiment of the invention can overcome the technical problems that the existing nano ZnO is easy to agglomerate and the like, obviously improves the performance of the uvioresistant or ultraviolet shielding material of the nano ZnO, and has good market prospect and social and economic benefits.

Fund project: the work subsidies national science fund projects (41972039, 41572038) and scientific research projects (16TD0011) funded by the university and development hall in Sichuan.

Claims (1)

1. A pyrophyllite loaded nano ZnO composite uvioresistant agent and a preparation method thereof are disclosed, natural flaky mineral pyrophyllite is used as a carrier mineral raw material, and a room temperature solid phase synthesis method is adopted to prepare the pyrophyllite loaded nano ZnO composite uvioresistant agent, which is characterized in that:

(1) preparing a zinc sulfate heptahydrate-pyrophyllite mixture: zinc sulfate heptahydrate (ZnSO)₄·7H₂O) and pyrophyllite mineral raw material in a mass ratio of 2-5: 1, respectively weighing a certain mass of heptahydrate zinc sulfate and pyrophyllite mineral raw material powder, and further grinding and mixing for 30-40 min to obtain a heptahydrate zinc sulfate-pyrophyllite mixture;

(2) preparation of a precursor zinc oxalate-pyrophyllite mixture: weighing a certain mass of sodium oxalate (Na) according to the molar ratio of zinc sulfate heptahydrate to sodium oxalate of 1-2: 1₂C₂O₄) And addAdding the mixture into a heptahydrate zinc sulfate-pyrophyllite mixture, and continuously grinding for 50-60 min to obtain a precursor zinc oxalate (ZnC)₂O₄·2H₂O) -pyrophyllite mixture;

(3) washing to remove impurities: carrying out centrifugal washing on a precursor zinc oxalate-pyrophyllite mixture by adopting a centrifugal washing device, washing with distilled water twice, and washing with absolute ethyl alcohol twice to remove impurities;

(4) drying the materials: transferring the washed and impurity-removed precursor zinc oxalate-pyrophyllite mixture into a drying device, wherein the drying temperature is 105 ℃, and the drying time is 3-6 h;

(5) roasting and loading: heating the dried precursor zinc oxalate-pyrophyllite mixture to 400-550 ℃ at the heating rate of 10-15 ℃/min in an air environment by adopting a roasting device, and preserving the heat for 2-4 h to obtain the pyrophyllite loaded nano ZnO composite uvioresistant agent.

The pyrophyllite is 2:1 type dioctahedral layered structure aluminosilicate mineral with a crystal chemical formula of Al₂[Si₄O₁₀](OH)₂The characteristic peak of the X-ray powder crystal diffraction analysis is

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